Saturated linear polyesters of mercaptodicarboxylic acids with dihydric alcohols



Patented Dec. 14, 1948 SATURATED LINEAR POLYESTERS .OF MER-e' CAPTODI'CARBOXYLIC ACIDS: WITH 'DI'-' HYDRIC'ALCDHOLS Burt" Carlton Pratt, Wilmington; Dela, assignr=tofi- E. I. 'du-Pont de Nemours'da {IfunparryyWilmington, per, a corporation ofl Delaware pplication Augustin, 1945',

Serial No. 610,402"

ficlaims. (Cl. 260--75) 1. This invention relatesto saturated linear poly esters containing thiol groups as lateral substituents'.

This application is a continuation in-part of my copending applicationSerial No. 519,647, filed January 25,1944.

This invention has as an object the provision of saturated linear polyesters of saturated aliphatic mercaptodicarboxylic acidswith saturated aliphatic dihydric alcohols, said esters containing thiol groups as lateral substituents. A'further object is the provision of polyesters of mercapto succinic acid withethylene glycol, said esters containing thiol-groups as lateral substituents.

A still-further object-isthe provision of methods for preparing the said new linear polyesters. Other objects will appear hereinafter.

These objects are-accomplished by the following invention" of saturated linear polyesters of saturated aliphatic *merc'aptodicarboxylic acids and saturated aliphatic dihydric alcohols and the preparation-thereof "by esterification of the dihydric alcohol with the mercaptodicarboxylic acid.

Inone. methodof practicing,- the invention, a

saturated aliphatic dihydric :alcohol is: reacted with an amount ofv the saturated aliphatic mercaptodicarboxylic acid required to yield a substantially neutral ester. Thus, for example, a

saturated linear polyester of: .mercaptosuccinic acid and ethylene glycol. is obtained by reacting equal molar amounts of the acid and alcohol until the desired degree of esterification has been obtained. The resulting linear polyester, when exposed to air in a thin film in the presence of about 0.10% of a suitable metallic drier forms films which are clear and tough. Upon baking at 100 C. hard films are obtained.

In the preparation of the saturated linear polyesters of this invention it is generally necessary to maintain an inert atmosphere during the esterification, for example, by passing carbon dioxide or nitrogen through or over the reaction mixture. Water formed during the esterification is continuously removed by an ordinary separator. After the desired degree of esterification has been obtained the reaction mixture is discharged from the reactor while still at substantially the reaction temperature.

The more detailed practice of the invention is illustrated in the following examples, wherein parts are by weight. There are, of course, many forms of the invention other than these specific embodiments.

Example 1 A mixture of 150 parts of monomercaptosuccinic acid and 62 parts of ethylene glylcol is placed in a reactor equipped with a stirrer, thermometer, condenser and an inlet tube for nitrogen, and the mixture heated for five hours at approx- 2; imately l50 c. under a blanket'of nitrogen. The acid number of the'cha'rge' is 585' and after-five hours itis 232 (using phenol-violet as indicator). The-product obtained isa stifi rubber-like, slightly tacky material-which is soluble in cyclohexanone.

Films cast from cyclohexanonesolutions and baked for 15' minutes-at l00-C; areslightly tacky and colorless. Baking overnight at C. gives very hard, tough, tack-free, Water-and alkaliresistant films. Addition o-f-'0.-l%"of cobaltas cobalt linoleate accelerates dryingso that after one hour at 100 C. afilmcontaining the cobalt is tack-free;

Duplication of the above example except-that succinic acid is used in place of monomercaptosuccinic acid-leads to the =forma'tion-of an" oily liquid which changes toa-stiff', greasy," paste; soluble in alcohol-toluene mixtures butnot'in tolu ene alone. A film of this product'shows no setup, even on 24 hoursbaking at 100 0."

Example.- -2 r A. mixture of 36.4 parts of. coconut "oil,j10.2 parts of glycerol "and 0iO3""part of litharge is pl'aced'in-the reactor described inEXample 1 and the mixtureheated for one hour at 200C. under a blanket of nitrogen. At the end of this-time the-reaction mixture is cooled to 35C; and 25 parts of monomercaptosuccinic acid isadded, the mixture heated'at 150C. and heating continued at this "temperature for 5 hours: Throughout this heating the reaction mixture is kept under a blanket of nitrogen. The product obtained is a clear, gel-like, tacky semi-solid at room temperature. The product analyzes 6.58% sulfur. The product is soluble in alcohol-toluene mixtures and cyclohexanone and fairly dispersible but not soluble in toluene. Films baked on glass overnight show good adhesion and are clear and water-white.

Ewample 3 A mixture of 19.6 parts of hexamethyleneglycol and 24.8 parts of monomercaptosuccinic acid is placed in the reactor described in Example 1 and heated at about C. for approximately 2 hours and 45 minutes. The product is colorless resin.

The saturated linear polyesters of this invention are the reaction products of a saturated aliphatic mercaptodicarboxylic acid with a saturated aliphatic dihydric alcohol. The mercaptodicarboxylic can be either a monomercapto acid, as exemplified by monomercaptosuccinic acid, 2- mercaptoadipic acid, 2-mercaptosebacic acid, Z-mercaptopimelic acid, etc., or it can contain a plurality of mercapto groups as lateral substituents in the saturated aliphatic chain, e. g.

2,3-dimercaptojsuccinic acid; 2,5-dimercaptoadipic acid, 2,9-dimercaptosebacic acid, etc.

The saturated, aliphatic dihydroxy alcohol can be either a glycol, e. g., ethylene glycol, propylene glycol, octamethylene glycol, decamethylene glycol, hexamethylene glycol, 1,12-octadecamethylene glycol, etc., or, as illustrated in Example 2, it can be a higher polyhydric alcohol in which all but two of the alcoholic hydroxyls have been esterified with a saturated aliphatic monocarboxylic acid, preferably an alkanoic acid. Suitable examples are the monoglycerides of hexanoic, octanoic, decanoic, dodecanoic, octadecanoic, and heXanoic acids, etc.

The examples have illustrated preparation of the saturated linear polyesters by reacting the acid with the saturated aliphatic dihydric alcohol. These esters can also be made by reacting the saturated aliphatic dihydric alcohol with an ester of the acid with a monohydric alcohol or by reacting the dihydric alcohol with theacid anhydride or halide. v

In the preparation of the saturated linear polyesters temperatures in the range of 120 to 200 C. are generally employed.

The saturated linear polyesters can be used either alone orin admixture with drying oils, natural orsynthetic resins, cellulose derivatives, etc. as coating compositions. To these compositions can be added pigments, dyes, fillers, driers, plasticizers, etc.

The invention is not limited to the exact details shown and described for obvious modifications will occur to persons skilledin the art.

What is claimed is:

1. A saturated linear polyester, having thiol groups as substituents on the linear chain, of substantially equimolecular amounts of a saturated aliphatic mercaptodicarboxylic acid containing only carbon, hydrogen, mercaptan sulfur and carboxyl oxygen with a saturated aliphatic dihydric alcohol containing only carbon, hydrogen and hydroxyl oxygen. v

2. A saturated linear polyester, having thiol groups as substituents on the linear chain, of substantially equimolecular amounts of mercaptosuccinic acid with a saturated dihydric alcohol 4 containing only carbon, hydrogen, and hydroxyl oxygen.

3. A saturated linear polyester, having thiol groups as substituents on the linear chain, of substantially equimolecular amounts of a saturated aliphatic mercaptodicarboxylic acid containing only carbon, hydrogen, mercaptan sulfur and carboxyl oxygen with ethylene glycol.

4. A saturated linear polyester having thiol groups as substituents on the linear chain, of substantially equimolecular amounts of mercaptosuccinic acid with ethylene glycol.

5. Process of preparing a saturated linear polyester, having thiol groups as substituents on the linear chain, of a saturated aliphatic mercaptodicarboxylic acid containing only carbon, hydrogen, mercaptan sulfur and carboxyl oxygen with a saturated aliphatic dihydric alcohol containing only carbon, hydrogen, and hydroxyl oxygen which comprisesreactlng as essentially the sole reacting ingredients, said acid with said alcohol at a temperature of at least C. in substantially equimoleoular quantity in an inert atmosphere, removing the Water formed in the reaction, and isolating the ester.

6. Process of preparing a saturated linear polyester, having thiol groups as substituents on the linear chain, of meroaptosuccinic acid with a saturated dihydric alcohol containing only carbon, hydrogen, and hydro-xyl oxygen which comprises reacting as essentially the sole reacting ingredients said acid with said alcohol at a temperature of at least 120 C. in substantially equimolecular quantity in an inert atmosphere, removing the water formed in the reaction, and isolating the ester.

BURT CARLTON PRATT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Martin Nov. 27, 1945 

